Rutgers researchers say ‘five-second rule’ isn’t safe

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Dropping food on the ground is an unfortunate occurrence, so understandably, some try to salvage those bites by picking up the morsels within the “five-second rule.”

But this week researchers at Rutgers University determined that this rule is really more of a myth.

They found that the combination of moisture, the type of surface and the contact time all contribute to cross-contamination. Frequently, contamination occurs in less than one second.

Rutgers professor and food science specialist Donald Schaffner said the rule is a “significant oversimplification of what actually happens when bacteria transfer from a surface to food.”

Boiled down, the researchers found that the rule is real in the sense that longer contact time results in more bacteria transferring to the piece of food. But other factors like the nature of the food, how wet it is and the type of surface it falls on are of “equal or greater importance.”

The research team tested four surfaces: stainless steel, ceramic tile, wood and carpet. They used four different foods: watermelon, bread, bread and butter and gummy candy.

They also tested four different contact times: less than one second, five seconds, 30 seconds and 300 seconds.

They then spread two different types of bacteria on the surfaces to see which food would get contaminated the most.

Watermelon had the most contamination and gummy candies had the least, according to their findings.

“Transfer of bacteria from surfaces to food appears to be affected the most by moisture,” Schaffner said. “Bacteria don’t have legs, they move with the moisture, and the wetter the food, the higher the risk of transfer. Also, longer food contact times usually result in the transfer of more bacteria from each surface to food.”

They also found that carpet has low transfer rates compared with tile and stainless steel. Wood is more variable, as the surface texture and the nature of the food can change the rate of contamination.